Conceptual design study of superconducting magnetic energy storage using high temperature superconductors

Since the discovery of high critical temperature superconductors (HTS), many predictions have been made for savings in the cost or performance of superconducting technologies for electric utility systems, such as superconducting magnetic energy storage (SMES). The higher operating temperature of HTS materials could mean the use of less expensive cryogens, such as liquid nitrogen, higher refrigeration efficiencies, greater reliability, and easier acceptance within the utility community. While all of these developments may occur, the significance of the improvements depends on the application and other characteristics of the system. Also, today's HTS materials have some negative features, including lower critical current density and greater brittleness, compared to conventional metallic superconductors. A conceptual design for SMES using HTS has been analyzed to determine configuration parameters, refrigeration requirements, and estimated costs of major components. The study covered the energy storage range from 2 to 200 MWh at power levels from 4 to 400 MW. This range includes utility applications from transient and power stabilization to spinning reserve and load leveling. The present assessment has been carried out for cold-supported modular torus and for comparison, a cold-supported modular solenoid. The toroidal configuration was chosen for analysis because it has minimal magnetic field, which couldmore » be an advantage in locating a small unit near a utility or customer load. The comparison shows that for all cases, the solenoid is comparable in price or less expensive. However, the solenoid has a varying external magnetic field which must be accommodated. The modular approach was selected primarily as a way to wind the coil and keep the brittle oxide superconductor under compression at all operating conditions to avoid breakage.« less